/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.nutch.crawl;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.nutch.util.ObjectCache;

/** Creates and caches a {@link FetchSchedule} implementation. */
public class FetchScheduleFactory {

	public static final Logger LOG = LoggerFactory
			.getLogger(FetchScheduleFactory.class);

	private FetchScheduleFactory() {
	} // no public ctor

	/** Return the FetchSchedule implementation. */
	public static FetchSchedule getFetchSchedule(Configuration conf) {
		String clazz = conf.get("db.fetch.schedule.class",
				DefaultFetchSchedule.class.getName());
		ObjectCache objectCache = ObjectCache.get(conf);
		FetchSchedule impl = (FetchSchedule) objectCache.getObject(clazz);
		if (impl == null) {
			try {
				LOG.info("Using FetchSchedule impl: " + clazz);
				Class<?> implClass = Class.forName(clazz);
				impl = (FetchSchedule) implClass.newInstance();
				impl.setConf(conf);
				objectCache.setObject(clazz, impl);
			} catch (Exception e) {
				throw new RuntimeException("Couldn't create " + clazz, e);
			}
		}
		return impl;
	}
}
